[Cryptech Tech] Happier RSA timing numbers

[Joachim Strömbergson]

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Aloha!

Rob Austein wrote:
>> After this the big thing I can do is the streaming interface I've
>> been talking about.
> ...
> 
> Sounds cool, but not sure it helps for specific case of AES keywrap. 
> You might want to look at sw/libhal/aes_keywrap.c (or the equivalent 
> Python implementation in the unit tests) as well as RFC 5649.

I'm fairly certain I was doing that, see mail from Yesterday:

"Looking at the code for aes_keywrap in:
https://trac.cryptech.is/browser/sw/libhal/aes_keywrap.c The inner
processing loop is at line number 199 (or 207)...."

> Basic problem I see is that the input to each ECB round in AES
> keywrap is a composite of two 64-bit fields, one of which is
> constructed by XORing a counter with 64-bits of the output of the
> previous round.  I see no obvious way to stream this.
> 
> One could of course use your streaming approach if the core were 
> performing the complete AES keywrap transform rather than just ECB.
> :)

Yes. And I think that might be the key here. I'll look a bit harder at
RFC 5649.

- -- 
Med vänlig hälsning, Yours

Joachim Strömbergson - Assured AB
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